Forecasting
weather can have its challenges, and meteorologists are generally limited
to a maximum range of between 11 to 14 days for making accurate forecasts
of future weather due to the complexity and chaos of the system. Predicting
future climate can be even more difficult.

Instruments such as rain
gauges and thermometers allow a high degree of accuracy in measuring
current weather conditions. In looking at past climate using paleo proxies
such as tree rings and ice cores there is some degree of uncertainty
in terms of how accurate the natural recorder is of the actual conditions
at the time. Likewise, in forecasting the future, there are unknowns
and uncertainties that scientists frame in terms of probability. Yet,
communicating probability without using numbers is not easy. A statement
such as "a high likelihood of drought conditions" is often
translated as "there will certainly be a drought" in the media.

One question that many people
are concerned with is whether or not global warming is occurring and
what the consequences will be. We know from current research that the
surface temperature of the Earth is warming, having risen by .6 degrees
Celsius over the past 100 years. (See Whitehouse
Press Release, June 2001). It is also known from ice core records
from Lake
Vostok in Antarctica that carbon dioxide emissions, primarily from
the combustion of fossil fuels, are at the highest levels in over 400,000
years.

What remains uncertain is how these increases of carbon dioxide-- an
important greenhouse gas-- and other human
impacts such as land use changes will react with naturally occurring
climate forces and variability in the future. Predictions of global
temperature increases vary, but various modeling scenarios run for the
Intergovernmental Panel on Climate Change (
IPCC) suggest a range of global warming of between 2.510.4°F
by 2100. How these changes will impact regional climate and hydrologic
dynamics is also largely uncertain.

Instrumental
records, while increasingly detailed and comprehensive, are often limited
to the past 100-150 years, and paleoclimate data enriches our understanding
of climate change by providing a longer term perspective of what is "normal"
or "average" in terms of climatic range and variability. Through
the Climate TimeLine's Data Access it is possible
to access instrumental data of your region of interest as well as examine
paleoclimate reconstructions for an overview
of recent centuries' climate variability. Also see A
Paleo Perspective on Global Warming and Global
Warming: Early Warning Signs from the Union of Concerned Scientists.